1. Field of the Invention
The present invention relates to a process for efficiently producing trans-type polyene antibiotics by irradiation with ultraviolet light, and the antibiotics produced by such a process. The substances obtained by the process of the present invention have antifungal activity and can thus be used as medical drugs, animal drugs, etc.
2. Discussion of the Background
As a polyene antibiotic having a cis-type polyene structure, partricin is known (J. Antibiotics, vol. 35, 997 (1982)). The stereo structure of polyenes, either trans-type or cis-type, is determined at the stage where these antibiotics are produced by microorganisms in fermentation solutions; and at present, it is extremely difficult to artificially change this stereo structure. However, it is known that when a diluted solution of partricin which is a cis-type polyene antibiotic is exposed to light, the maximum absorption wavelength in the ultraviolet region is shifted by 4 nm to the longer wavelength region. It is considered that this wavelength shift occurs because cis-type partricin is changed to trans-type (U.S. Pat. No. 3,773,925; issued Nov. 20, 1973).
In general, polyenes are very unstable to exposure to light. For example, as described in the literature supra, even though a partricin solution is simply exposed to light, conversion into trans-type occurs and at the same time, the formed trans-type compound is decomposed so that the product is finally completely decomposed. Thus, any case where the trans-type compound obtained by the photoreaction is isolated as a chemically pure substance is unknown. In addition, no processes which are utilized for the industrial production of trans-type antibiotics by exposure to light are known. Thus, there remains a need for a process for efficiently converting cis-type polyene antibiotics into trans-type polyene antibiotics in a simple manner.